Nitrocellulose containing adhesive compositions

ABSTRACT

A NITROCELLULOSE CONTAINING ADHESIVE COMPOSITION COMPRISING TWO COMPONENTS WHICH ARE MIXED TOGETHER AND CURED. COMPONENT A COMPRISES NITROCELLULOSE, METRIOL TRINITRATE AND ETHYL CENTRALITE WHILE COMPONENT B COMPRISES TRIETHYLENE GLYCOL DINITRATE, ETHYL CENTRALITE AND DIBUTYLTIN DILAURATE. THE INVENTION ALSO INCLUDES THE METHOD OF APPLYING THE COMPOSITION TO THE SYSTEM TO BE USED, NAMELY THE MIXING OF THE TWO COMPONENTS TOGETHER AND APPLYING TO THE SURFACES TO BE ADHERED BEFORE THE MIXTURE COMPLETELY CURES.

United States Patent Olfice 3,758,325 Patented Sept. 11, 1973 3,758,325NIT ROCELLULOSE CONTAINING ADHESIVE COMPOSITIONS Craig E. Johnson,Indian Head, and Larry D. Henderson,

Bryans Road, Md., assignors to the United States of America asrepresented by the Secretary of the Navy No Drawing. Filed June 23,1972, Ser. No. 265,934 Int. Cl. C08]: 21/12, 27/42, 27/52 US. Cl.106-480 8 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTIONIn various ordnance devices, such as ammunition and propellant chambers,adhesives had heretofore been used to adhere various parts together. Forexample, cartridge devices are often glued together by first filling thepropellant chamber with propellant granules and then affixing the backportion of the device onto the chamber by means of a conventional gluesuch as an epoxy resin.

However, these epoxy resins suffer from a disadvantage in that theyleave a residue after the propellant is ignited. A residue is leftbecause these epoxy resins, as is true of other conventional glues, arenot energetic. In addition, many of the prior art adhesives suffer fromthe fact that the bonds they form are not elastic since the adhesivedoes not contain a plasticizer. Furthermore, many present adhesivescontain a solvent and this causes degradation of the product as well ascracking of the adhesive bond.

SUMMARY OF THE INVENTION Accordingly,

It is one object of this invention to obtain an energetic adhesive.

It is another object of this invention to provide an adhesive whichundergoes clean burning.

It is yet another object of the present invention to obtain an adhesivewhich burns rapidly.

A further object of this invention is to obtain an adhesive bond whichdoes not crack.

An additional object of the invention is to produce an adhesive whichdoes not undergo a degradation.

It is still another object of the instant invention to formulate a curedadhesive which is flexible.

It is even another object of the instant invention to obtain an adhesivewhich is strong.

These and other objects are accomplished by providing a two componentcomposition, which, upon admixture, forms an excellent adhesive whichmust be applied prior to the time it takes for it to be cured. ComponentA comprises pelletized or plastisol nitrocellulose, metriol trinitrate[hereinafter MTN] and ethyl centralite [hereinafter EC] while componentB comprises dibutyltin dilaurate [hereinafter DBTDL], EC, andtriethylene glycol dinitrate [hereinafter TEGDN].

DESCRIPTION OF THE PREFERRED EMBODIMENTS The adhesive of the instantinvention is formed by mixing two separate components, which shall becalled Components A and B. While each of the components are stable andmay be stored for extended. periods, when they are mixed together, theywill cure in anywhere from a few minutes to a few days, depending uponvarious conditions. The curing, in large part, depends upon the amountof TEGDN present in component B. The TEGDN is a plasticizer and the moreplasticizer that is present, the quicker the cure and, therefore, theshorter the pot life, or allowable usage life, of the mixture. Anadditional plasticizer, such as adiponitrile may be present in componentB in amounts from 0 to about 10 percent by weight of the composition ofcomponent B. Adiponitrile is a more active plasticizer than TEGDN and asa result the pot life of the mixture will decrease at a greater ratewith increasing amounts of adiponitrile than it would for increasingamounts of TEGDN. With no adiponitrile present, the cure time at roomtemperature is about three days, while about ten percent adiponitrilewill decrease the cure time at room temperature to about 6-8 hours. Curetime may also be decreased by an increase in temperature to a value notto exceed F.With no adiponitrile present in the composition, heating themixture to 140 F. will decrease the cure time to two to four hours. (If10 percent adiponitrile is present, the cure time at 140 F. is a fewminutes.

The mixture must be applied during the pot life of the mixture. Themixture can be applied to either a rubber or metal surface, but whenapplied to a metallic surface, a primer of cellulose acetate in acetoneis first applied and the adhesive will bond to this.

Component A comprises, on a weight percent basis, 20-80% of pelletizedor plastisol nitrocellulose, 2080% of MTN and 0.1 to 2% of EC. Apreferred composition contains about 48.5% of plastisol nitrocellulose,49.87% of MTN and 1.63% of EC. Component -B comprises, on a weightpercent basis, from about 0.005% to 0.3% DBTDL, which serves as acatalyst for crosslinking; 0.1 to 2% of EC; which serves as astabilizer; and a balance of TEGDN. A preferred composition contains99.74% of TEGDN, 0.25% EC and 01% DBTDL. Component B can also contain,as optional ingredients, up to 10% of adiponitrile (plasticizer); up to50% of MTN; up to 3% of fibrous nitrocellulose [as a thickener]; up to1% of a standard coloring agent; and up to 0.2% of resorcinol, which isused as a stabilizer for any ammonium perchlorate oxidizer system thatthe adhesive may come in contact with during use. These optionalingredients are added to the composition as a replacement for part ofthe TEGDN.

Components A and B are to be stored in separate containers. Shortlybefore they are to be used they are mixed in a ratio of component A tocomponent B between about 3.34:1 to about 2:1. It is desirable, but notnecessary, to vacuum degas the mixture prior to use so as to prevent airinclusion in the bond, thus promoting higher shear strength.

The following example will serve to better illustrate the invention.This example is not intended to limit, in any manner, the scope of theinstant invention or the claims to follow.

Example Component A is comprised of 48.5% of plastisol nitrocellulose,49.87% of MTN and 1.63% of EC. The mixture, which can be formulated inany conventional manner [which is true of component B as well], isprepared as follows.

The ingredients are dried to a moisture content of 0.2 percent or lessprior to mixing. The PNC and MTN are vacuum mixed in the presence of atleast four percent by weight of heptane. The ingredients can be mixed atany temperature up to 140 F.

Component 13 comprises 99.74% TEGDN, .25% EC and .01% DBTDL. Theingredients are dried to a moisture content of 0.2 percent or less priorto mixing. Mixing is time dependent and agitation throughout the mixingcycle is not necessary. When component B is completely mixed, it will befree-flowing and transparent. Mixing temperature is not to exceed 140 F.

Twenty-five parts of component B are mixed with fifty parts (by weight)of component A. The mixture has a pot life of 4-8 hours and a 4 hourcure time at 140 F. Tensile strength exceeds 50 p.s.i.

The mixture can be used to glue together the parts of an ordnance systemas Well as to glue one type of rocket propellant to another. Forexample, it can bond together a single base propellant to a double basepropellant, or a double to a double or a. single to a single. When thepropellant is burned, so is the adhesive as it burns rapidly andcleanly, leaving no residue.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeunderstood that within the scope of the appended claims the inventionmay be practised otherwise than as specifically described herein.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. An adhesive composition which is the product of the process of mixinga component A with a component B wherein said component A comprises,

on a weight percent basis, 2080% of metriol trinitrate,

0.1 to 2% of ethyl centralite and 20-80 percent of said nitrocellulosecompound, and wherein said component B comprises, on a weight percentbasis, from .005-.3 percent of dibutyltin dilaurate, 0.1-2 percent ofethyl centralite and a remainder of triethyleneglycol dinitrate.

2. The composition of claim 1 wherein said component B also comprisesfrompercent of adiponitrile, from 0-30 percent of metriol trinitrate,from 0-3 percent of fibrous nitrocellulose, from 0-1 percent of acoloring agent, and from 0.2 percent of resorcinol.

3. The composition of claim 1 wherein component A comprises 48.5 percentof plastisol nitrocellulose, 49.87 percent of metriol trinitrate and1.63 percent of ethyl centralite; and wherein component B comprises .01percent of dibutyltin dilaurate, 0.25 percent of ethyl centralite, and99.74 percent of triethylene glycol dinitrate.

4. A composition useful in producing an adhesive composition, whichconsists essentially of on a weight percent basis, 20-80% of metrioltrinitrate, 0.1 to 2% of ethyl centralite and 20-80 percent of saidnitrocellulose compound.

5. The composition of claim 4, consisting essentially of: 48.5 percentof plastisol nitrocellulose, 49.87 percent of metriol trinitrate and1.63 percent of ethyl centralite.

6. A composition useful in preparing adhesives, which comprises, on aweight percent basis, from .005-.3 percent of dibutytin dilaurate, 0.1-2percent of ethyl centralite and a remainder of triethyleneglycoldinitrate.

7. A composition according to claim 6, comprising: .01 percentdibutyltin dilaurate, 0.25 percent ethyl centralite and 99.74 percenttriethyleneglycol dinitrate.

8. A composition according to claim 6, which also comprises from 0-10percent of adiponitrile, from 0-30 percent of metriol trinitrate, from0-3 percent of fibrous nitrocellulose, from 0-1 percent of a coloringagent, and from 0-2 percent of rcsorcinol.

Chem. Abstr., vol. 34: 6075 1940. Chem. Abstr., vol. 49, 7035 1955.

THEORDORE MORRIS, Primary Examiner US. Cl. X.R.

